1. Field of the Invention
The present invention relates generally to improved data migration for archived information, and in particular, but not exclusively to, an improved system and method for migrating digital medical patient image data from one long-term storage media to a second long-term storage media.
2. Background of the Invention
Picture Archiving and Communication Systems (PACS) are data storage environments that can be used to acquire, manage and display medical diagnostic image information about patients. Typical PACS provide picture viewing capabilities at diagnostic and reporting workstations, archiving on magnetic or optical media for short-term or long-term storage, communications using Local Area Networks (LANs), Wide Area Networks (WANs) or publicly-available communications services, and modality interfaces and gateways to healthcare facility and departmental information systems. A primary goal of most PACS users is to convert their traditionally film-based image departments to film-less or nearly film-less operations.
A significant problem that exists in this field relates to the long-term storage and management of the digital image data. As digital image storage technologies evolved, prudent data storage managers found it necessary to migrate their image data from older storage media to newer long-term storage environments. For example, as the known DLT-2000 magnetic tape cartridge storage media became obsolete, data storage managers found it necessary to transfer their image data from DLT-2000 tapes to the next generation tape storage media. In fact, the need to transfer or migrate patient image data from older to newer storage media typically arises numerous times during the legal retention times required for the patient image data involved.
FIG. 1 depicts a pictorial representation of a conventional process for migrating digital patient image data from one long-term data storage media to another (e.g., newer) long-term data storage media. The process shown in FIG. 1 illustrates a conventional approach for storing patient image data in a typical PACS environment. As such, to implement process 100, medical diagnostic imaging scanners and devices such as, for example, Magnetic Resonance Imaging (MRI) scanner 102, Computer Tomography (CT) scanner 104, and x-ray, ultrasound and mammography film digitizing devices (e.g., 106) can generate patient diagnostic image data in digital form. Typically, in order to retain the patient image data for legally prescribed periods of time, the digital image data from scanners 102, 104 and/or digitizing device(s) 106 is formatted in accordance with the Digital Imaging and Communications in Medicine (DICOM) protocol (indicated by arrow 108), and transferred via conventional communications network 110 to PACS Archive 112. For example, communications network 110 may be a LAN, WAN, the Ethernet, the Internet, or any other publicly- or commercially-available communications network capable of conveying image data in digital form.
Once PACS Archive 112 receives and stores the transferred image data in DICOM form, the data can then be stored for finite periods of time on local disk cache 114. For example, the storage media used for local disk cache 114 can be fast magnetic disk, dense magnetic disk, or any other appropriate data storage technology. Periodically, a Hierarchical Storage Manager (HSM) application being executed by an operating system in PACS Archive 112 migrates the data from local disk cache 114 to long-term archive 116, which is controlled by this HSM application. For example, long-term archive 116 can be implemented as a tape library or optical “jukebox”.
Typically, HSM applications are data storage systems that are used to automatically move data between high-cost and low-cost storage media. Data managers often use HSM applications for organizational data migration, because high-speed storage devices (e.g., hard disk drives) are significantly more expensive (e.g., per byte stored) than slower storage devices (e.g., magnetic tape drives or optical discs). HSM applications can be used to store most of an organization's data on the slower, less expensive media, and then copy the data to the more expensive, high-speed disk drives as needed. As such, an HSM can effectively convert an organization's high-speed storage devices into one or more caches for the slower storage devices.
Typically, PACS Archive 112 maintains a database with an index of patient demographics and the location or address where this data is stored in long-term archive 116. For example, the patient index information can include an identifier (e.g., number) associated with the storage media used, and an address for the location of the data stored on that media.
Various processes may be used to migrate data from a long-term storage device to another long-term storage device. For example, a data manager can have PACS Archive 112 initiate a process to retrieve patient data from (internally-controlled) long-term archive 116, and then send the data (e.g., via network 110) to a second (externally-controlled) long-term storage device. Typically, as illustrated by FIG. 1, the migrating data can be sent to a server associated with “external” HSM application 118. Examples of such “external” HSM applications are an Archival Storage Manager-Unix (ASM-Unix) application and/or server produced by Storage Technology Corporation, a Tivoli Storage Manager (TSM) application and/or server produced by IBM Corporation, or an HSM application and/or server produced by several other corporations.
As the data is migrated to “external” HSM application 118 (e.g., as indicated by arrow 122), the data is typically transferred in a non-DICOM format. A non-DICOM format commonly used for transferring data is the Binary Large Object (BLOB) format, which can represent data as a single entry from the internal database of PACS Archive 112. A BLOB format is often used in order for a data manager to provide allowances for image consolidation, loss-less image compression factors, and relative ease of access to “external” HSM archives.
External HSM application 118 receives and stores the migrated image data (e.g., in BLOB form). The received data can then be stored for finite periods of time on local disk cache 120. Periodically, external HSM application 118 migrates the data from local disk cache 120 to long-term archive 124, which is typically controlled by external HSM application 118.
The specific order in which patient data is migrated from one storage device (e.g., long-term archive 116) to another (e.g., long-term archive 124) can be based on a number of different factors. For example, the data may be migrated based on time stamps that identify when the data was stored. As such, a first-in, first-out (FIFO) or last-in, first-out (LIFO) migration approach may be used. Also, the data may be migrated on a patient-by-patient basis or patient classification basis (e.g., patient study-by-study basis).
In any event, as the patient data is migrated or transferred to external HSM application 118, the patient index information maintained in the database of PACS Archive 112 is updated as each unit of data is moved. This update approach enables PACS Archive 112 to still use the data during the typically extensive period while the migration is being performed. Nevertheless, a significant drawback of these conventional migration processes is that they are relatively inefficient, because the order in which the patient data is retrieved from long-term archive 116 is typically unrelated to the arrangement or layout of the data in the storage media involved. Consequently, the conventional data migration processes are inefficient and resource consuming (e.g., in terms of excessive computer, server, and network processing time, and long-term storage resources being inefficiently used). In fact, the typical data transfer rate of the conventional migration processes is approximately 5-20 Gbytes per day. As such, an average data migration process may take several weeks to complete. In a relatively large archive environment (e.g., >4 Tbytes), the data migration process can take up to several years.
Therefore, it would be desirable to have a method and system for increasing the data transfer rates and efficiencies of processes used for migrating digital data from one long-term storage media to a second long-term storage media, such as, for example, a PACS patient image data migration process.